Does anyone know what the cylindrical part of the 8.1s Horizon water pump does? I replaced impeller on starboard engine, re-attached hoses and I can’t get the water shooting out the side of boat, I actually pulled the pump twice (to review my work) as it didn’t work the first time, and it’s not working now. Hoses connected correctly. Impeller and o-ring in the housing seated correctly. Sea cock open. Sea strainer full of water. What am I missing?